[BUG]: Audio track does not work properly，when the video track is turned off。

Package version

3.0.0-pre.7

Environment

* OS:Windows10
* Unity version: Unity 2021.3

Steps To Reproduce

1. open audioTrack
2. close videoTrack

Current Behavior

Audio track does not work properly，when the video track is turned off，but when I turn on the video track ，audio track works properly，show my code：
var configuration = GetSelectedSdpSemantics();
localPeerConnection = new RTCPeerConnection(ref configuration);
pcOnIceConnectionChange = state => { OnIceConnectionChange(localPeerConnection, state); };
pcOnIceCandidate = candidate => { OnIceCandidate(localPeerConnection, candidate); };
pcOnNegotiationNeeded = () => { StartCoroutine(PeerNegotiationNeeded(localPeerConnection)); };
AudioStreamTrack audiotrack = new AudioStreamTrack(audioTrack);
VideoStreamTrack track = Capture_Camera.CaptureStreamTrack(146, 146);
var sendStream = new MediaStream();
localPeerConnection.AddTrack(audiotrack, sendStream);
localPeerConnection.AddTrack(track, sendStream);

Expected Behavior

I want to use Audio track only because of the limited hardware environment。

Anything else?

No response